[plt-dev] Symptom of REPL's hopelessness?

On Oct 1, 2009, at 4:19 PM, Robby Findler wrote:

> What is the difference between generate-temporaries and gensym?

'generate-temporaries' returns identifiers that don't have an  
associated '#%top' binding, but 'gensym' returns a symbol, which gets  
coerced into an identifier using the lexical context of the 'with- 
syntax' form, which does have a binding of '#%top' in scope.

Ryan


> On Thu, Oct 1, 2009 at 3:11 PM, Sam TH <samth at ccs.neu.edu> wrote:
>> On Thu, Oct 1, 2009 at 4:01 PM, Casey Klein
>> <clklein at eecs.northwestern.edu> wrote:
>>> Can someone explain why this macro expands without error in a module
>>> but not in the REPL?
>>>
>>> (define-syntax (m stx)
>>>  (syntax-case stx ()
>>>   [(_ x)
>>>    (with-syntax ([(y) (generate-temporaries (syntax (x)))])
>>>      (syntax (define (y) y)))]))
>>>
>>>> (m q)
>>> compile: unbound identifier (and no #%top syntax transformer is  
>>> bound) in: q1
>>
>> This version of the macro works:
>>
>> (define-syntax (m stx)
>>  (syntax-case stx ()
>>  [(_ x)
>>   (with-syntax ([(y) (list (gensym (syntax-e #'x)))])
>>     (syntax (define (y) y)))]))
>>
>> --
>> sam th
>> samth at ccs.neu.edu
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